import java.util.Scanner;

// 动态规划基础题，爬楼梯最小花费
// 状态表示：dp[i]表示到达i位置时的最小花费
// 状态转移方程：dp[i] = min(dp[i-1]+cost[i-1], dp[i-2]+cost[i-2])
public class Main2 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] cost = new int[n];
        for (int i = 0; i < n; i++) {
            cost[i] = scanner.nextInt();
        }

        if (n == 1) {
            System.out.println(cost[0]);
            return;
        }

        int[] dp = new int[n+1];
        for (int i = 2; i <= n; i++) {
            dp[i] = Math.min(dp[i-1]+cost[i-1], dp[i-2]+cost[i-2]);
        }

        System.out.println(dp[n]);
    }
}